Optical oxygen sensing based on the luminescence change of metalloporphyrins immobilized in styrene–pentafluorostyrene copolymer film

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Abstract
A series of new fluoropolymers, poly(styrene-co-pentafluorostyrene) (poly-Styn-co-PFSm) with different ratios of Sty and PFS units, were synthesized and applied as an optical oxygen sensing matrix using phosphorescence quenching of metalloporphyrins, platinum and palladium octaethylporphyrin (PtOEP and PdOEP), by oxygen. The phosphorescence intensity of PtOEP of PdOEP in poly-Styn-co-PFSm films decreased with increase in oxygen concentration. The ratio I0/I100 was used to express the sensitivity of the sensing film, where I0 and I100 represent the detected phosphorescence intensities from a film exposed to 100% argon and 100% oxygen, respectively. For PtOEP in poly-Styn-co-PFSm films, the I0/I100 values were >24.0 and large Stern–Volmer constants of >0.23%−1 were obtained compared with PtOEP in PS films. For PdOEP in poly-Styn-co-PFSm films, on the other hand, large I0/I100 values of >92.0 are obtained. However, the Stern–Volmer plots of PdOEP in poly-Styn-co-PFSm films exhibit considerable linearity at lower oxygen concentrations between 0 and 20%. These results indicates that PtOEP and PdOEP films are useful optical oxygen sensors for oxygen concentrations between 0 and 100% and between 0 and 20%, respectively. No effect of the ratio of Sty to PFS units in poly-Styn-co-PFSm and on the oxygen sensing properties of PtOEP and PdOEP were observed. The response times of PtOEP and PdOEP immobilized in poly-Sty1-co-PFS0.21 films were 5.6 and 3.0 s on going from argon to oxygen and 30.0 and 90.1 s on going from oxygen to argon, respectively. This result indicates that PtOEP and PdOEP immobilized in poly-Styn-co-PFSm films represent a highly sensitive device for oxygen.